This invention relates to containers or carriers for goods of the kind in which the goods are enclosed in a flexible or partly flexible sealed envelope or skin, the container being partly evacuated of air so that the skin is caused, under the action of external atmospheric pressure, to embrace and hold the goods together or to hold them onto a rigid support within or forming part of the envelope. Such a container or carrier is described for example in British Pat. No. 1,191,921 and U.S. Pat. Nos. 3,850,214 and 3,000,481.
By using this kind of container, a stable and compact package is obtained which facilitates transportation or handling of the goods. Such containers find particular application in the carriage of goods by aircraft since they enable goods to be held rigidly and firmly without needing the construction of containers specially shaped to fit the goods and without excessive weight.
It is often necesssary to avoid any severe shocks to goods and it is known therefore to provide shock-absorbing mounts for goods in such containers. In such cases, it often becomes important that the vacuum within the envelope should be limited to avoid pulling the cover too hard down so that the shock-absorber mounts are highly compressed. Generally speaking, adequate holding of the goods in position is obtained with only a relatively small vacuum. Typically the reduction in pressure might be of the order of 11/2 to 4 lb per sq. inch, i.e., 10,000 to 30,000 N/m.sup.2 which is only a small fraction of atmosphere. This is one example of circumstances in which it is desirable to ensure adequate control of the vacuum pressure, even although wide variations can be tolerated. On the other hand, failure of the vacuum would result in absence of any restraint holding down the goods. This has to be avoided in many circumstances.